Gas effusion studies of oxygen-doped cuprates

Abstract

We have studied oxygen evolution, as a function of increasing temperature, of four oxygen-doped high T c cuprates. The oxygen effusion spectra of La 2CuO 4+δ, YBa 2Cu 3O 6+δ, HgBa 2CuO 4+δ, and Bi 2Sr 2CaCu 2O 8+δ share unusually similar two-peak feature. Although excess oxygen ions (δ) occupy different crystallographic sites in different systems, i.e., interstitial site in La 2CuO 4+δ and Bi 2Sr 2CaCu 2O 8+δ, CuO chain in YBa 2Cu 3O 6+δ, and “normal” lattice site in HgBa 2CuO 4+δ, the oxygen atoms evolve in two distinct steps upon heating. Considering the strong coupling between excess oxygen ions and doped holes, we suggest that this two-peak feature is intrinsic to the doped holes of all high T c cuprates.